Relationships

Toad Data Modeler allows you to design Entity Relationship Diagrams of specific database platforms, convert physical model from one database platform to another, create an ER Diagram directly from your database (Reverse Engineering feature), update physical models, generate DDL/SQL scripts and Change Scripts, create Dictionary Types, Views, Triggers, Functions, generate detailed documentation to your model (in HTML, RTF, PDF, XSLT formats) and much more.

This chapter describes features and functions related to Physical Data Modeling. Look around each section to get the information you need.

Benefits of Physical Data Model

• Detailed definition of database structure, including database specific items, for example:
  • Stored procedures
  • Functions
  • Triggers
  • Views
  • Materialized views
  • Sequences (auto increments) etc.
• Possibility to synchronize local model with existing database.
• Possibility to specify logical names for objects (captions for tables, attributes and other objects).
• Detailed database specific information can be exported to HTML/RTF/PDF or XML/XHTML/CSV reports.
• Automatic generation of SQL code for selected objects (SQL code generation is not available in Logical and Universal Model)
• Automatic migration of PK attributes to child entities (Attributes don't migrate to child entities in Logical Model)

Notation and Cardinality

IE Notation

Cardinality

One-to-many relationship is represented by this symbol:

One-to-one relationship is represented by this symbol:

Parent: mandatory Child: mandatory

Parent: mandatory Child: optional

Parent: optional Child: mandatory

Parent: optional Child: optional

IDF1X Notation

Cardinality

,  ,   zero, one or more

one or more

zero or one

Parent: mandatory Child: mandatory

Parent: mandatory Child: optional

Parent: optional Child: mandatory

Parent: optional Child: optional

See Synchronization of Not Null and Mandatory Parent for more information.

Relationship Types

Identifying Relationship

Non-identifying Relationship

Non-identifying Self-relationship

M:N Relationship

Relationship Types

Toad Data Modeler supports the following relationship types (physical model):

• Identifying
• Non-identifying
• Self-relationship for non-identifying relationship
• M:N relationship

Identifying Relationship

Primary key migrates from parent entity to child entity and there becomes a part of the primary key. It is used when the primary key of the child entity is unable to provide definite identification.

An entity, connected with a parent entity through an identifying relationship, is called "dependent" entity and is shown in a model with rounded corners.

The Order Record entity cannot exist itself. It is dependent on entities Customer and Film. Therefore the Identifying relationship is used. The Order Record entity is a dependent entity, and the Customer ID and Movie ID items are its unique record identifiers.

Non-Identifying Relationship

Primary key migrates from parent entity to child entity and does not become a part of the primary key. Non-identifying relationships are represented by dashed lines. In the dependent table, the attribute is referred to as a foreign key.

The Film ID as the unique identifier for Film is sufficient. Therefore the non-identifying relationship is used. The Genre ID is only a foreign key. The film can exist without being assigned to a genre, therefore the Film entity is an Independent entity.

Self-Relationship for Non-identifying Relationship

M:N Relationship

Create Relationships

1. Select a relationship type - click the appropriate relationship icon on the toolbar:

 Identifying relationship (also CTRL+R)

 Non-identifying relationship

   M:N relationship

2. Move your mouse cursor over the work area. (The cursor changes its appearance.)
3. Click the first entity (parent) and then the target entity (child).

To create self-relationship for non-identifying relationship

1. Click the Non-identifying relationship icon on the toolbar .
2. Move your mouse cursor over the work area.
3. Double-click the selected entity on the Workspace.

To add multiple relationships

1. Press SHIFT and click the Relationship icon. See the blue frame in the icon now.
2. Create as many relationships in you model as you need.
3. Right-click the work area (or click the Relationship icon again) to turn this function off.